[MBreve]

Okay, I understand.

In this case, all traffic from 10.0.0.10 will nerver route over the ISP B.

But where does NAT come in?

You wrote that Routing is done after the packets went through CP. I have now client side NAT which would mean that the packet is already translated before it goes to routing. And the Source 10.0.0.10 is already translated to the Public IP adres.